1. Field of the Invention
The invention pertains to the art of making basically aluminum heat exchangers and pertains in particular to a method of making such a coil in which copper transition members such as inlet and outlet tubes are soldered ultrasonically at the same time that all-aluminum other joints are being soldered in an ultrasonic soldering bath.
2. Description of the Prior Art
U.S. Pat. No. 3,833,986 discloses an arrangement for ultrasonically soldering telescopic joints of a basically all aluminum coil, the gist of that invention being the provision of an aperture in the bight end of a hairpin tube to provide venting for the tubing to atmosphere during the ultrasonic soldering process. That patent also suggests that in a prior art process, a practice was utilized in which special vent tubes were inserted into the free ends of the serpentine tubing (i.e., the ends to which inlet and outlet copper tubes are usually typically connected after the ultrasonic soldering), and shaped with angularly turned remote ends projecting out of the solder bath, like snorkel tubes, to communicate the interior of the serpentine tubing with atmosphere so that solder would flow into the telescopic joints. This process is suggested as having difficulties in that the special vent tubes were thereby soldered into the free ends of the serpentine tubing, but were not necessary nor usable in connection with the refrigerant circuit and as a result it was necessary to reform or remove the special tubes involving considerable time and expense.
In the known commercial art of which I am aware, the practice has been to provide a coil arrangement in which the hairpin-shaped tubes, and return bends and other fittings were arranged so that the free ends of the serpentine tubing to which inlet and outlet connections of copper tubing would ultimately be made were located at the end opposite that end which was immersed in the ultrasonic soldering bath. Then, after the ultrasonic soldering had occurred, the copper inlet and outlet tube arrangements were connected to the free ends of the tubes and the soldering was then done manually and individually for each connection. One reason for doing this was that if the inlet and outlet tube arrangements were of manifold character, in which branch tubes were bonded as by brazing to a suction header or expansion device means, the material of the brazed joint would contaminate the ultrasonic solder bath and render it unfit for use in time.
The aim of my invention is to provide a method for making an aluminum heat exchanger coil in which the copper inlet and outlet tube arrangements are soldered to the heat exchanger at the same time and in the same ultrasonic soldering bath in which the solder joints of the hairpin tubes and return bends are made.